"554 5.7.9: Message not accepted for policy reasons" when sending email to Yahoo"
Gee, thanks yahoo!.
For many years, I've been emailing various folks on Yahoo!, and I give as my from-address, an aol.com address, because that's what they're expecting, and where they should send any replies.
Suddenly, as of about a month ago, Yahoo! have implemented DMARC. This checks that emails really did come from the address they claimed to come from. And since my emails didn't really come from AOL, they got rejected.
"We recently changed our DMARC policy to proactively protect our users
from increasing email spam that uses Yahoo users’ email addresses from
other mail servers."
Well, 10/10 for trying to protect your users from spam. But I really don't think that this will do it. All it's going to do, is annoy legitimate email senders like me, that have been sending Yahoo! users email for the last 17 years, and now suddenly can't. It took me a few minutes to work out what I had to change, and a few seconds to make the change, but I think that most people caught by this, aren't going to be able to work out what to do. And Yahoo! users won't get emails that could be important.
The spammers, of course, thoroughly understand the email system, and will know immediately what to do. Duh.
The spam problem comes about because the cost of sending, transmitting and receiving spam doesn't fall on the spammer. It's borne by everyone else. So, it costs almost nothing to send a million emails, and a response rate of one in a million is good enough. And that's why you get so much spam. Indeed, about half the spam I get, I couldn't read even if I wanted to, because it's in Chinese, or Russian where I can't even understand the alphabet. Or a foreigh language where I can read it, but can't understand it.
Once you've understood the cause of the spam problem, the answer becomes obvious. If spammers had to pay, say, 0.1p for each email sent, then a million emails would cost £1000, and a one-in-a-million success rate wouldn't be enough. They'd have to target their emails a lot more carefully. Instead of me getting a torrent of Viagra offers, I'd only get emails offering useful parts for bikes.
Of course, that means that normal users have to pay too. But since I send maybe 100 emails per week, the 10p cost wouldn't cause me a problem. I'd willingly pay that to avoid emails with subjects like "三連複がアツい♪【6月15日（日）第19回マーメイドス", "Polizza Auto? Salva un Preventivo e scopri se hai vinto 100 euro in Buoni" or even "Find the greatest solution to all your health wants".